1. Field of the Invention
The present invention relates to a developing unit, and more particularly to a developing unit which is used in a color image forming device to which toner is externally supplied.
2. Background Information
Image forming devices that use an electrophotographic system are provided with, for example, a charging unit, an exposure unit, a developing device, a transfer device, and a cleaning device at the circumference of a photoreceptor drum (an image carrier). In addition, a fusing device is provided on the downstream side of the photoreceptor drum in the transfer material transport direction. First, with such an image forming device, the charging unit uniformly charges the surface of the photoreceptor drum. Subsequently, the exposure unit exposes the photoreceptor drum based on image data, and thereby forms an electrostatic latent image on the photoreceptor drum surface. The developing device then develops the electrostatic latent image.
If the image forming device is a full color type, then four developers are provided that respectively contain a cyan, a magenta, a yellow, and a black developing agent, which develop those four colors of the toner image. Subsequently, the developed toner image is transferred by the transfer device onto a transfer material and then fused by the fusing device, after which the transfer material is discharged to a discharge unit. The cleaning means cleans the residual developing agent on the photoreceptor drum.
The development of the toner in such an image forming process consumes the toner contained in the developers, making it necessary to supply toner. One method of supplying toner consumed by image formation is to externally supply toner by providing a toner container that is external to the developers, as disclosed in Japanese Published Unexamined Patent Application No. H10-198149. In this publication, toner is supplied to a plurality of developing devices by inserting a toner supply member into the developing device of each toner color to be supplied.
With a device of a type that supplies toner by inserting a toner supply member into a developing device as disclosed in Japanese Published Unexamined Patent Application No. H10-198149, if the device transitions to an electric power cutoff state during the toner supply operation, then the operation of the developing device will stop in a state wherein the toner supply member is inserted in a developing device. When the supply of power subsequently resumes, there is a risk that the state wherein the toner supply member is inserted into the developing device will not be recognized and, in such a state, the developing device will rotate in order to initialize. In such a case, there is a possibility that the toner supply member or the developing device will break.
An object of the present invention is to prevent breakage of the toner supply member and the developing device when the supply of power resumes, even if electric power was cut off in a state wherein the toner supply member was inserted in the developing device.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need to prevent breakage of the toner supply member and the developing device when the supply of power resumes, even if electric power is cut off in a state wherein the toner supply member was inserted in the developing device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.